How flexible is Front End DTI with excellent credit and 40% down?

[Ian James]

We charged forth with a home but stumbled when we learned our initial tax obligation calculation was $400 a month lower than reality, crimping our DTI and mortgage figures. With 780+ credit and 40% down coming from our own home sale proceeds, using our current lender's "customer for life" program to re-apply, and with perfect payment performance over 8 years with them, is the 28% front end DTI written in stone, or is there flexibility? How much flexibility? Our back end debt is zero. Standard 30y conventional. Thanks.